The present invention relates to a method and a device for automatically detecting an incorrect measurement of a total temperature on an aircraft.
It is known that an aircraft, in particular a transport airplane, uses temperature and pressure data, and notably the total temperature TAT (Total Air Temperature), which are measured by on-board air data probes, for a plurality of applications such as the calculation of the airspeed for control of the flight and for display in the cockpit, engine control and the management of the power of the engines, etc.
The management of the power of an engine is generally implemented by an electronic full authority digital engine control system of the FADEC (Full Authority Digital Engine Control) type, which is responsible for the control and monitoring of the engine with which it is associated. The FADEC system generally comprises a control computer of the EEC (Electronic Engine Control) type as its main computer. The control of the engines requires three air data parameters in order to regulate the appropriate thrust of the engine: the static pressure Ps, the total pressure Pt and the total air temperature TAT of the air around the skin of the fuselage of the aircraft. These three air data parameters are used for calculating the following parameters: the standard altitude ISA, the Mach number Mn and the temperature difference ΔISA between the current temperature and the standard temperature. A power management table is integrated in the EEC computer in order to provide the relationship between the ambient conditions (ISA, Mn, ΔISA) and the engine control parameter (N1, EPR, TPR) which is controlled by the EEC computer. The taking into account of an exact value for each of the three primary data parameters (Ps, Pt, TAT) is essential in order to be able to adjust the required thrust.
The total temperature is measured using a plurality of temperature probes arranged on the skin of the fuselage of the aircraft so as to measure the temperature of the airflow. These temperature probes comprise temperature-sensitive components which change resistance in response to temperature changes.
However, incorrect measurement of total temperature can appear when there is presence of frost or of ice crystals. It is known that icing is a meteorological phenomenon, the conditions for the appearance of which are related to the humidity and to the static temperature. Icing can have effects on the probes, which can be sufficient to degrade the measurement, sometimes making it incorrect (frozen or biased).
In order to solve this problem, the probes are heated in order to prevent such icing which can compromise their reliability.
Even though the deicing means are efficient, it is not possible to completely prevent cases of icing of some of the probes among the plurality of probes which equip an aircraft, for example in the case of incorrect operation of the deicing means or possibly in the presence of ice crystals.
It is therefore advantageous to be able to have means available on the aircraft making it possible to detect, in real time and in a reliable manner, any incorrect measurement of the total temperature provided by a temperature probe in the presence of icing conditions in order to prevent the systems of the aircraft from using such an incorrect measurement.